Reference is made to French Patent No. 81 12770 published on Jun. 29, 1981 and relating to a system for treating flue gases from gas fired burners and No. 88 11 651 published on Sep. 6, 1988 and relating to the concept used on direct contact heaters. This is considered to be the closest prior art and it teaches an arrangement of a second and a third packing section within a system which operates as a water vapor pump for the treatment of exhaust flue gases at the outlet of a boiler and for the further treatment of combustion air at the entrance of the boiler. The system described relates to the exchange of heat and condensate for humidifying drying and heating cooling gases by an exchange system.